which brush number for a spatter cap airbrush as one moves along ?

Hi,

I see a spatter effect tool , one click and its a spatter with varying size dots and varying opacity.

but as soon as I drag the tool along I get the exact same pattern laid down repeatedly so it becomes a streak with normal dense centre.

I want what might be termed a spatter cap airbrush, as you spray from left to right you get dots of varying sizes appear, not a continous line. and not a repeat pattern, so just like the real thing.

I am doing edges of small waves, wanting to paint along the edge and get water spatter.

I could dip a toothbrush in white paint and finger tip stroke it using a frisket mask if it was a painting or scale model, but I also would reach for my spatter cap and fit it to the airbrush, adjust the pressure and spatter it., moving left to right.

Which tool number and settings gives this ?

I am CS6

Cheers

Merlin